Synthesis of amorphic and hexagonal boron nitride via high temperature treatment of NH3BH3 and Li(BH3NH2BH2NH2BH3)

Abstract

Thermal decomposition of NH₃BH₃ and Li(BH₃NH₂BH₂NH₂BH₃) was investigated at temperatures up to 1000 °C under various conditions with an inert atmosphere. It was found that complete dehydrogenation of ammonia borane towards amorphous boron nitride (a-BN) occurs at 850 °C when using monel reactors or at 1000 °C with the hot isostatic pressing method (HIP), which is significantly lower than was earlier reported. Li(BH₃NH₂BH₂NH₂BH₃) was found to decompose towards hexagonal boron nitride (h-BN) at 1000 °C with the HIP method but at 850 °C in monel reactors towards a mixture of a-BN and h-BN. The findings are confirmed by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM).